1. Field of the Invention
The present invention generally relates to ophthalmological instruments and, more particularly, to a computer-controlled electro-optical instrument designed to automate and quantify clinical examination of pupillary responses and extrinsic eye muscle balance. The invention is specifically directed to an optical system for such an instrument which simultaneously focuses images of a patient's left and right pupils on different areas of a common photosensitive image plane of a video camera. The two images are located close to one another and greatly magnified on a display screen to allow the physician to better observe and analyze pupil response to stimuli.
2. Description of the Prior Art
The iris of the eye is (in humans) a ring-shaped colored muscle. The hole in the center of the iris, called the pupil, normally appears black because the surfaces behind it reflect back to an observer much less light than does the surrounding iris. When the eye is suddenly exposed to light, certain of the muscle fibers in the iris contract, causing the pupil to become smaller, or constrict. The pupils also constrict when a near object is viewed, and their diameter is also determined continuously by certain aspects of psychological state, for example, fear. Pupil diameter is also affected by the actions of many drugs, both systemic drugs and those applied directly to the eye.
The overall physiological system that controls pupil size includes many components, and because the various components may be affected in various ways by different diseases, toxins, tumors, and the like, disorders are often reflected in abnormal pupillary responses. Therefore, examination of the responses of the pupillary system is an important part of most neurological and ophthalmological medical examinations. To perform an examination of pupil responses, the physician dims the room lights, illuminates one eye and then the other with a small light, and observes the responses. This technique, even when performed by the most careful observer, lacks much in accuracy and provides no quantitative or permanent record of the results.
Various systems are known in the prior art which automate the examination of pupil function and provide a quantitative result. For example, U.S Pat. No. 3,036,568 to Stark shows a pupillometer which monitors the response of an eye to light stimulus. An infrared light source is used to illuminate the eye. A glow lamp provides a visible light stimulus and, as a result of a constriction of the pupil, the light reflected from the iris to an infrared sensitive device varies. The output of the infrared sensitive device is supplied to a chart recorder. In U.S. Pat. Nos. 3,533,683 and 3,533,684, Stark et al. show a dynamic pupillometer using a television camera system in which an infrared light source, a visual light stimulator and a television camera system are all directed at the eye of a patient. As in the previous Stark patent, the pupil contracts upon visual light stimulation thus allowing the iris to reflect more infrared light, but in this case the infrared light is detected by the camera. The instantaneous pupil size is determined by counting television scan lines.
Other examples of automated pupil function examination systems are disclosed in U.S. Pat. No. 3,966,310 to Larson which shows a hand held pupillometer and U.S. Pat. No. 4,755,043 to Carter which shows a digital portable scanning pupillometer.
It is also known to automate other eye examination procedures. For example, U.S. Pat. No. 4,370,033 to Kani et al. discloses an eyeball examining device which is used to analyze the eye retina. A visible light beam is projected onto any area of the eye retina, and a magnified image of the eye retina is displayed on an infrared television monitor. U.S. Pat. No. 4,618,230 to Ens et al. discloses a computer controlled visual stimulator that obtains an electroretinogram by an automated process.
While there exist several systems that address the problem of automating the examination of the pupil function, the scope of the examination is relatively limited and requires a highly skilled person to operate the system and analyze the results.